Photo-flash bulb



Nov. 15, 1955 H. MARTIN PHOTO-FLASH BULB Fild July 50, 1951 INVENTORHERMANN MARTIN AGENT United States Patent 9 PHOTO-FLASH BULB HermannMartin, Hamburg-Wandsbek, Germany, assignor to Hartford National Bank &Trust Company, Hartford, Conn., as trustee Application July 30, 1951,Serial No. 239,212 Claims priority, application Germany September 20,1950 9 Claims. (CI. 67-31) This invention relates to a photo-flash bulbto be ignited electrically. Such photo-flash bulbs are known to comprisean envelope which encloses a material adapted to be burnt with theradiation of actinic light and which contains in addition an electricigniting mechanism.

The electric igniting mechanism generally comprsies one or morefilaments which are connected by means of current supply wires to twocontacts provided on the cap of the photo-flash bulb. The actinicallyreacting material is ignited by the filament being brought toincandescence by means of electric current so that, for example, anignition paste is ignited and the combustion of the actinically reactingmaterial is thus initiated.

In order that the ignition may be started with sufiicient rapidity theelectric current must not be excessively low. Generally, a current from0.3 to 0.5 ampere is required for this purpose but this also depends onthe thickness and the composition of the ignition filaments. If lowercurrents are used ignition of the photo-fiash bulb does not ensue at allor ensues with time-lag. In the latter case synchronisation between theshutter of the camera and the combustion of the actinically reactingmaterial is not sufiiciently accurate so that light radiation does notensue wholly or in part until, after opening, the shutter of the camerahas closed.

This difficulty occurs, for example, when for the purpose of igniting aphoto-flash bulb use is made of alargely exhausted electrochemicalsource of energy, for example an electric cell.

Such cells are known to be used frequently for the ignition ofphoto-flash bulbs, the same cell being used many times. Exhaustion ofthe electric cell can be ascertained by the photographer withdifficulty, only, since testing with the use of a small electricincandescent lamp, as often effected for checking a cell, is not areliable indication whether the cell is still capable of supplying thecurrent required for the ignition in due time of a photo-flash bulb.

The invention embodies a photo-flash bulb to be ignited electrically,the envelope of which encloses a material adapted to be burnt with theradiation of actinic light and to be ignited by means of an electricallyheated filament, and is characterised in that the photo-flash bulb, forexample its cap, accommodates an electrochemical source of energy whichis capable of supply a quantity of electrical energy, sulficient foronce igniting the photoflash bulb within the short time required forignition.

The invention is based on recognition of the fact that the electriccurrent required for once igniting the photofiash bulb, is required tobe maintained for such a short period only that a comparatively lowamount of energy from about to 50 mw./sec. is given off and thatelectric sources of energy capable of transiently supplying thisquantity of energy may be small enough to be readily accommodated in thecap of a photo-flash bulb. Thus, for example, it has been found,according to the invention, that an electric cell of suificient powerfor this purpose can be manufactured by severing from a commerciallyobtainable cell a portion the electrode surface area of See which is 3cm For this purpose a portion 5 mms. in length may be severed from acylindrical cell of the Danish mark Hellesens having a section of 19mms. After its end faces have been sealed this cell may be incorporatedin the cap of a photo-flash bulb. The internal diameter of the cap is 22mms. The positive terminal of the cell is connected to the bottomcontact in the cap. The other (negative) terminal is soldered to one ofthe current supply wires. The other current supply wire is connected tothe cap wall.

For the purpose of igniting the paste, two tungsten wires having alength of 3 mms. and a diameter of 11 mms. are connected to the twocurrent supply Wires. Upon connection of the two contacts on the cap inan electrically conductive manner the photo-flash bulb is ignited atonce and measuring the igniting rate does not reveal any re tardation ofthe ignition.

However, as is well-known many electrochemical cells have no keepingqualities so that after having been stored for a period their power isaffected. A delayed ignition may ensue when the photo-flash bulbaccording to the invention has been stored for a period.

According to the invention a cell is preferably incorporated whichbecomes operative immediately before ignition due to the electrolytebeing transferred from a particular tank to the cell.

In order that the invention may be more clearly understood and readilycarried into effect, it will now be described in greater detail withreference to the accompanying drawing, in which examples of preferredembodiments of the invention are shown.

Fig. 1 is a cross-sectional view of a flashlamp embodying the presentinvention,

Fig. 2 is a top plan view of the electrolyte tank therein,

Fig. 3 is a modification of the device embodying the present invention,

Fig. 4 is a top plan view of the electrolyte tank shown in Fig. 3.

A highly preferred embodiment of the invention is obtained withphoto-flash bulbs by accommodating the powerful cell within the cap andin addition by using the internal surface of the cap as one of theelectrodes of the cell. For this purpose it is preferable that theinternal surface of the cap should be coated with a galvanic zinc layerabout 20 in thickness. The counter electrode may be constituted by anoxidised lead foil about 0.1 mm. thick. The lead foil may be coiled upto form a cylindrical body and be gripped in the cap, a cellulosestripserving as the intermediate layer.

Referring to Fig. l, as outlined hereinbefore, the cap 1 is internallycoated with a zinc layer 2. The intermediate layer is designated 3 andthe oxidised lead foil 4. Extending through the cap bottom is a movablestud 5 which is electrically insulated relatively to the cap and whichserves as the bottom contact of the cap. In addition it constitutes thecontrol member by which the electrolyte tank 8 can be acted upon, forexample smashed. The stud 5 is connected to a disc 6 which on the studbeing forced inwards engages with the electrolyte tank. The electrolytetank itself rests upon the element 7. The supply wires of the helicalfilament are connected on the one hand to the electrode 4 which is madeof oxidised lead foil and on the other hand to the contact stud 5, forexample by soldering. When the control member 5 is moved inwards bymanual compression or by screwing in of the lamp into the socket, theelectrolyte tank 8 is smashed and the electrolyte liquid reaches in theshortest time possible the preferably perforated lead bioxide foil andsoon penetrates through the absorbing intermediate layer 3 into thespace intermediate the electrodes so that the galvanic element is inreadiness to become operative.

The stud 5 is preferably such that even after termination of itsinwardly directed movement it remains a predetermined distance from thecap bottom to and in addition engages with the central part of thesocket.

The electrolyte tank may be constituted for example by an annular glasstube such as in Fig. 2 or by a helically wound glass tube such as inFig. 3. As an alternative, the material of such electrolyte tanks may bea brittle synthetic substance which is capable of holding theelectrolyte liquid without any substantial reaction on said tanks, orelse it may be a ceramic material. When using an electrolyte tank ofceramic material the parts of the wall which face the active spaceintermediate the electrodes may readily be made thinner, for example bygrinding, so that upon exertion of pressure by the control member theyare smashed prior to the remaining parts of the wall and a directionaleffect for the electrolyte liquid is thus produced.

It is advisable for the electrolyte liquid in the electrolyte tank to bemaintained under pressure in order to ensure a given squirting effect,or a rapid flowing away of the electrolyte liquid from the tank.Pressure above atmospheric pressure may be produced, for example, byintroducing a zinc pastille or a piece of zinc wire after filling theelectrolyte tank to capacity and sealing the tank only subsequently. Theaction of the electrolyte liquid on the zinc will then result in knownmanner in the production of hydrogen which brings about an appreciableincrease in pressure so that when the Walls of the electrolyte tank arebeing smashed, the electrolyte impinges forcibly upon the electrodesurfaces.

The ignition of a photo-flash bulb is effected by the stud 5, which alsoserves as a bottom contact and is connected to one supply wire for thehelical filament, being electrically connected to the cap wall. Asmentioned hereinbefore, the cap wall constitutes one electrode of thecell. The counter electrode, that is to say, the oxidised lead foil isconnected to the second supply wire of the helical filament. Theconnecting lead between the members 5 and 1 preferably includes a switchby means of which ignition is struck.

With the embodiment shown in Fig. 4 like parts are designated byreference similar to those in Fig. 1. The construction shown in Fig. 4differs from the embodiment shown in Fig. 1 in that a horizontallylocated cell insulated relatively to the cap wall is provided with oneelectrode being constituted by an oxidised lead foil 4 and the otherelectrode 2.2 being made of Zinc. The electrolyte tank 8a is shaped inthe form of a circular ring. It is located immediately below the controlmember 5 or below the disc 6 connected to this member. As soon as theelectrolyte tank is smashed and the electrolyte liquid has got into thespace intermediate the electrodes, ignition may be initiated byestablishment of an electrical connection between the control member 5and the cap 1, preferably by way of a switch. The control member 5 orthe disc 6 is connected to one electrode 4 of the cell. The supply wiresfor the helical filament are secured on the one hand to the secondelectrode 2a and on the other hand to the cap 1. In the two embodimentsshown in Figs. 1 and 4 provision is made laterally in the wall of thecap of an aperture 9 which is covered by a preferably transparent plate10. This plate 10 is prepared in such manner that it shows a change incolour upon engagement with the electrolyte liquid. This provides anindication perceptible from without whether the powerful cell maypossibly be already consumed. For preparing the plate 10 use may be madeof any of the numerous indicating devices known in experimentalchemistry, with which we are concerned as a rule with organic dye stuffsthe colouring of which depends on the hydrogen ion concentration andwhich consequently indicate an acid, neutral or alkaline reaction bychange in colour.

What I claim is:

1. A photo-flash bulb adapted to be ignited electrically comprising'anenvelope composed at least partially of.

a light transmitting material provided with a cap, a substance enclosedby said envelope and adapted to be ignited electrically and burned whileradiating actinic light, an electrochemical source of energy including afrangible container having a liquid electrolyte therein in said capbeing an integral part of said bulb and which is capable of supplying aquantity of electrical energy sufiicient for igniting once thephoto-flash bulb within the short time required for ignition, ignitingmeans, and connecting leads for connecting said igniting means to saidelectrochemical source of energy.

2. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, a substance enclosed by said envelope andadapted to be ignited electrically and burned while radiating actiniclight, an electrochemical source of energy in said cap comprising aclosed frangible tank containing electrolyte liquid, and means actuatedfrom the outside of said bulb for crushing said tank whereby saidelectrolyte liquid is transferred immediately before ignition from saidtank to the remainder of said area within said cap, igniting means, andconnecting leads for connecting said igniting means to saidelectrochemical source of energy.

3. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, a substance enclosed by said envelope andadapted to be ignited electrically and burned while radiating actiniclight, an electrochemical source of energy in said cap comprising a tankfor electrolyte liquid whereby said electrolyte liquid is transferredimmediately before ignition from said tank to the remainder of said areawithin said cap, said tank being composed of a brittle, syntheticmaterial which is substantially non-reactive to said electrolyte liquid,igniting means, and connecting leads for connecting said igniting meansto said electrochemical source of energy.

4. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, a substance enclosed by said envelope andadapted to be ignited electrically and burned while radiating actiniclight, an electrochemical source of energy in said cap comprising afrangible tank for electrolyte liquid maintained at above-atmosphericpressure by a zinc pastille therein whereby said electrolyte istransferred immediately before ignition from said tank to the remainderof said area within said cap, igniting means, and connecting leads forconnecting said igniting means to said electrochemical source of energy.

5. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, said cap having its internal surface coatedwith a galvanic metal layer which serves as one electrode of saidphotoflash bulb, a substance enclosed by said envelope and adapted to beignited electrically and burned while radiating actinic light, anelectrochemical source of energy in said cap comprising a frangible tankfor electrolyte liquid whereby said electrolyte liquid is transferredimmediately before ignition from said tank to the remainder of said areawithin said cap, igniting means, and connecting leads for connectingsaid igniting means to said elec trochemical source of energy.

6. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, a substance enclosed by said envelope andadapted to be ignited electrically and burned while radiating actiniclight, an electrochemical source of energy in said cap comprising afrangible tank for electrolyte liquid and a metal stud extending througha wall of said cap and insulatingtherefrom whereby when a force isexerted on said stud in a predetermined direction said tank is shatteredthus permitting the electrolyte liquid from said tank to penetrate theremainder of said area with said cap, igniting means, and connectingleads for connecting said igniting means to said electrochemical sourceof energy.

7. A photo-flash bulb as claimed in claim 6 wherein said stud isprovided with a pin positioned transversely of the longitudinal axis ofsaid stud and externally of said cap for limiting the movement of saidstud in said predetermined direction.

8. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap, said cap having its internal surface coatedwith a galvanic metal layer which serves as one electrode-of saidphoto-flash bulb, a substance enclosed by said envelope and adapted tobe ignited electrically and burned while radiating actinic light, anelectrochemical source of energy in said cap comprising a frangible tankfor electrolyte liquid and a metal stud serving as the other electrodeof said photo-flash bulb and extending through a wall of said cap andinsulated therefrom whereby when a force is exerted on said stud in apredetermined direction said tank is shattered thus permitting theelectrolyte liquid from said tank to penetrate the remainder of saidarea within said cap, igniting means, and connecting leads forconnecting said igniting means to said electrochemical source of energy.

9. A photo-flash bulb adapted to be ignited electrically comprising anenvelope composed at least partially of a light transmitting materialand provided with a cap having an aperture in one Wall thereof, asubstance enclosed by said envelope and adapted to be ignitedelectrically and burned while radiating actinic light, anelectrochemical source of energy in said cap comprising a frangible tankfor electrolyte liquid whereby said electrolyte liquid is transferredimmediately before ignition from said tank to the remainder of said areawithin said cap, an indicator plate covering said aperture and showing achange in color upon contact with said electrolyte liquid, ignitingmeans, and connecting leads for connecting said igniting means to saidelectrochemical source of energy.

References Cited in the file of this patent UNITED STATES PATENTS1,853,968 Pagan Apr. 12, 1932 2,118,996 Winckler May 31, 1938 2,147,116Winckler Feb. 14, 1939 2,561,532 Muir July 24, 1951 FOREIGN PATENTS431,953 Great Britain July 18, 1935

